Laminating adhesive, laminate including the same, and method of making a laminate

ABSTRACT

Disclosed is a method of making a laminate that includes a) preparing an adhesive composition, where the preparing includes combining a first part that includes (meth)acrylate functional, polyisocyanate prepolymer, and polyisocyanate monomer, the first part including at least 10% by weight isocyanate functional groups, and a second part that includes polyol, at least one of the first part and the second part includes photoinitiator, b) coating a first flexible substrate with the adhesive composition, c) exposing the adhesive composition to radiation to partially cure the adhesive composition, and d) contacting the adhesive composition with a second flexible substrate.

BACKGROUND

The invention relates to preparing dual cure laminating adhesives, andlaminates including the same.

Flexible packaging materials are widely used in a variety of areasincluding food packaging. Flexible packaging is often constructed fromfilm laminates in which a layer of laminating adhesive is disposedbetween a first film (e.g., a polyethylene terephthalate, polyamide orcellophane film) and a second film. Laminates are often used in foodpackaging because a desired film property cannot be achieved with asingle layer or type of film. By combining films having differentproperties in the form of a laminate, a desired property or combinationof properties can be achieved.

Laminates are typically constructed to have a strong cured bond that isresistant to delaminating stresses resulting from differences in modulusof the laminae, as well as to the added stresses imposed in the use ofthe laminate including exposure to heat, cold and humidity. Substratesused in food laminates often include metallized surfaces and/or have lowsurface tension, to which it is difficult to form a strong bond Variousadhesives have been developed for use in preparing laminates includingsolvent based, water based, two component solventless adhesives, andradiation curable adhesives. Organic solvents such as methyl ethylketone, ethyl acetate, and alcohols, which are used in some laminatingadhesives, tend to be flammable and may pose environmental concerns.Therefore it is desirable to use solventless laminating adhesives.Water-based laminating adhesives, which often include aqueousdispersions of polyurethane and other components, require theexpenditure of heat to remove the water.

Because conventional two-component laminating adhesives often requirestorage for a prolonged period before exhibiting sufficient strength topermit handling and further processing, various efforts have been madeto decrease the rate of cure for laminating adhesives. Areas in whichrecent efforts have been focused include electron beam and ultraviolet(UV) curable adhesive compositions. Although radiation curing canincrease the rate of cure, processes that use such techniques do notalways produce an adhesive and/or a laminate with suitable properties.Electron beam radiation, for example, can undesirably degrade the heatseal properties of certain films.

SUMMARY

In one aspect, the invention features a method of making a laminate thatincludes a) preparing an adhesive composition, where the preparingincludes combining a first part that includes (meth)acrylate functional,polyisocyanate prepolymer, and polyisocyanate monomer, the first partincluding at least 10% by weight isocyanate functional groups, a secondpart that includes polyol, and optionally a third part, at least one ofthe first part, the second part and the optional third part includingphotoinitiator, b) coating a first flexible substrate with the adhesivecomposition, c) exposing the adhesive composition to radiation topartially cure the adhesive composition, and d) contacting the adhesivecomposition with a second flexible substrate.

In one embodiment, the first part includes at least 15% by weight thepolyisocyanate monomer. In another embodiment, the first part includesat least 30% by weight the polyisocyanate monomer. In other embodiments,the exposing occurs prior to contacting the adhesive composition withthe second flexible substrate. In some embodiments, the exposing occursafter contacting the adhesive composition with the second flexiblesubstrate.

In another embodiment, the adhesive composition exhibits a viscosity offrom 250 centipoise to 5000 centipoise at a temperature from 65° F. to170° F.

In some embodiments, the coating includes coating the adhesivecomposition at a coating weight of from 0.5 pounds per 3000 square feetto 4 pounds per 3000 square feet.

In other embodiments, the adhesive composition exhibits a lap shearstrength of at least 25 g/in² after exposure to the radiation. In oneembodiment, the adhesive composition exhibits a lap shear strength of atleast 100 g/in² after exposure to the radiation.

In other embodiments, the adhesive composition includes from 5% byweight to 70% by weight the (meth)acrylate functional, polyisocyanateprepolymer, at least 7% by weight the polyisocyanate monomer, from 30%by weight to 95% by weight the polyol, and from 0.2% by weight to 10% byweight the photoinitiator. In another embodiment, the first part of theadhesive composition includes from 40% by weight to 90% by weight the(meth)acrylate functional, polyisocyanate prepolymer, and from 10% byweight to 60% by weight the polyisocyanate monomer. In some embodiments,the first part of the adhesive composition includes from 10% by weightto about 20% by weight isocyanate functional groups. In otherembodiments, the first part includes from about 0.5% by weight to about20% by weight radiation polymerizable groups. In one embodiment, thefirst part includes from about 1% by weight to about 10% by weightradiation polymerizable groups.

In another embodiments, the first part and the second part are combinedin amounts such that the stoichiometric ratio of isocyanate (NCO) tohydroxyl group (OH) (NCO:OH) is from about 1:1 to about 2:1.

In some embodiments, the (meth)acrylate polyisocyanate prepolymerincludes the reaction product of a) an isocyanate polyurethaneprepolymer includes the reaction product of i) polyol and ii)isocyanate, and b) hydroxy functional (meth)acrylate. In one embodiment,the hydroxy functional acrylate includes hydroxyalkyl (meth)acrylate. Inanother embodiment, the hydroxy functional acrylate includeshydroxyethyl acrylate.

In other embodiments, the polyol includes polyester polyol, polyetherpolyol, or a mixture thereof. In one embodiment, the polyol has afunctionality of at least 2. In other embodiments, the polyol has afunctionality of no greater than 3.

In some embodiments, the adhesive composition includes from 20% byweight to 95% by weight polyol. In another embodiment, the adhesivecomposition includes from 30% by weight to 70% by weight polyol.

In other embodiments, the adhesive composition includes from 30% byweight to 70% by weight the (meth)acrylate functional, polyisocyanateprepolymer. In some embodiments, the adhesive composition includes from20% by weight to 60% by weight the (meth)acrylate functional,polyisocyanate prepolymer.

In one embodiment, the photoinitiator is selected from the groupconsisting of dialkoxy acetophenones, hydroxyalkyl phenyl ketones,benzoin ethers, benzoin acetals, acyl phosphine oxides, and combinationsthereof. In another embodiment, the photoinitiator includes a hydroxylfunctional photoinitiator.

In one embodiment, at least one of the first and second flexiblesubstrates is a polymer film. In some embodiments, at least one of thefirst and second flexible substrates is a metal foil.

In other embodiments, at least one of the first flexible substrate andthe second flexible substrate includes polyethylene terephthalate,polypropylene, polyethylene, metallized polypropylene, metalizedpolyethylene terephthalate, Nylon, and metal foil.

In one embodiment, the method of making a laminate includes a) coating afirst flexible substrate with an adhesive composition that includes(meth)acrylate functional, polyisocyanate prepolymer, at least 7% byweight polyisocyanate monomer, polyol, and photoinitiator, b) exposingthe adhesive composition to radiation to partially cure the adhesivecomposition, and c) contacting the adhesive composition with a secondflexible substrate.

In another embodiment, the method of making a laminate includes a)preparing an adhesive composition, the preparing includes combining afirst part that includes (meth)acrylate functional, polyisocyanateprepolymer, and at least 15% by weight polyisocyanate monomer, and asecond part that includes polyol, at least one of the first part and thesecond part includes photoinitiator, b) coating a first flexiblesubstrate with the adhesive composition c) exposing the composition toradiation to partially cure the composition, and d) contacting theadhesive composition with a second flexible substrate.

In other embodiments, the method of making a laminate includes a)preparing an adhesive composition, the preparing includes combining(meth)acrylate functional, polyisocyanate prepolymer, polyisocyanatemonomer, the combination of the prepolymer and the monomer including atleast 10% by weight isocyanate functional groups based on the combinedweight of the prepolymer and the polyisocyanate monomer, polyol, andphotoinitiator, b) coating a first flexible substrate with the adhesivecomposition, c) exposing the adhesive composition to radiation topartially cure the adhesive composition, and d) contacting the adhesivecomposition with a second flexible substrate.

In another aspect, the invention features a laminate that includes anadhesive composition that includes the reaction product of(meth)acrylate functional, polyisocyanate prepolymer, polyisocyanatemonomer, the combination of the prepolymer and the monomer including atleast 10% by weight isocyanate functional groups based on the combinedweight of the prepolymer and the polyisocyanate monomer, polyol, andphotoinitiator, a first flexible substrate, and a second flexiblesubstrate, the first flexible substrate being bonded to the flexiblesubstrate through the adhesive composition.

In one embodiment, the laminate includes an adhesive composition thatincludes the reaction product of a (meth)acrylate functional,polyisocyanate prepolymer, polyisocyanate monomer, polyol, andphotoinitiator, a first flexible substrate, and a second flexiblesubstrate, the first flexible substrate being bonded to the secondflexible substrate through the adhesive composition, the adhesivecomposition exhibiting a destructive peel to at least one of the firstand second substrates.

In other aspects, the invention features a package that includes a) afood article, and b) a laminate described herein at least partiallysurrounding the food article.

The invention features a method of making a laminate in which theadhesive of the laminate exhibits sufficient green strength to permithandling and further processing prior to being fully cured. Theinvention also features a method of making a food laminate in which theadhesive of the laminate exhibits a faster rate of cure relative toexisting two-component food laminating adhesives. As a result, theperiod of storage required before the laminate can be used is decreasedrelative to manufacturing processes that use existing food laminateadhesives. In addition, because the laminate may undergo furtherprocessing relatively soon after it has been prepared, the storagerequirements associated with the laminate are reduced relative to thoserequirements for existing two component food laminate adhesives. Therelatively fast rate of cure of the adhesive also decreases, and canprevent, adhesive from seeping through pinholes in the film layers andsmearing of the ink present on one or more of the film layers of thelaminate. The adhesive composition also has a viscosity at the coatingtemperature that provides good wet out onto various substrates used inlaminates.

The adhesive composition also exhibits good adhesion to difficult toadhere to substrates including, e.g., metallized substrates andsubstrates that exhibit low surface tension, i.e., a surface tensionless than 34 dynes/cm².

Other features and advantages will be apparent from the followingdescription of the preferred embodiments and from the claims.

GLOSSARY

In reference to the invention, these terms have the meanings set forthbelow:

The term “(meth)acrylate” refers to acrylate, methacrylate, and mixturesthereof.

The term “dual cure” refers to a composition that cures through twodifferent mechanisms, e.g., radiation and a reaction between isocyanatefunctional group(s) and hydroxyl group(s).

DETAILED DESCRIPTION

The method of making the laminate includes coating a first flexible filmsubstrate with an adhesive composition that includes a 100% solids twopart dual cure composition, exposing the coated composition toradiation, and contacting the adhesive composition with a secondflexible film substrate. Exposing the adhesive composition to radiationcan occur before, during, or after, and combinations thereof, contactingthe adhesive with the second flexible film substrate. The adhesivecomposition can be directly exposed to radiation or exposed to radiationthrough at least one of the substrates, where the substrate issufficiently transparent to ultraviolet radiation. Exposing the adhesivecomposition to radiation initiates free radical polymerization of theradiation curable functional groups present in the composition, whichimparts initial adhesive properties, e.g., green strength, to thelaminate. A relatively slower reaction involving the isocyanate groupsand the hydroxyl groups present in the composition also occurs over timeand provides the final performance properties of the adhesivecomposition and a laminate constructed therewith. Without wishing to bebound by theory, the present inventors believe that the presence of theunsaturation, and the initiation of free radical cure, speed the rate ofcure that occurs between the isocyanate and hydroxyl groups.

The adhesive composition is a dual cure adhesive composition thatincludes a first part, Part A, which includes a radiation polymerizablepolyisocyanate prepolymer and polyisocyanate monomer, and a second part,Part B, which includes polyol. The adhesive composition also includesphotoinitiator, which may be present in Part A, Part B, or a combinationthereof. Alternatively, the photoinitiator may be provided to thecomposition separate from Part A and Part B. Part A and Part B of thecomposition are preferably combined to achieve a stoichiometric ratio ofisocyanate (NCO) to hydroxyl group (OH) (i.e., NCO:OH) of from about 1:1to 2:1, from 1.2:1 to 1.6:1, or even about 1.4:1. Part A and Part B arepreferably combined in amounts such that, prior to cure, the compositionincludes at least about 5% by weight, at least about 30% by weight, atleast about 50% by weight, at least about 60% by weight, no greater thanabout 80% by weight, or even no greater than about 70% by weightradiation polymerizable polyisocyanate prepolymer, at least 5% byweight, at least 10% by weight, no greater than about 50% by weight, nogreater than about 40% by weight, or even no greater than about 30% byweight polyisocyanate monomer, at least about 20% by weight, at leastabout 30% by weight, no greater than about 90% by weight, or even nogreater than about 70% by weight polyol, and from 0.2% by weight toabout 10% by weight, or even from 0.5% by weight to 1% by weightphotoinitiator.

Parts A and B of the composition are combined with mixing prior tocoating. When Part A and Part B are combined, the composition preferablyhas a viscosity of from 250 centipoise to 5000 centipoise at atemperature from 65° F. to 170° F. The two parts of the dual curecomposition then react with each other over time forming crosslinks. Therate at which this reaction occurs impacts the pot life, i.e., theperiod during which the composition can be coated and used for itsintended purpose, of the dual cure composition. Preferably the dual curecomposition exhibits a pot life of at least 30 minutes, or even at least45 minutes. As indicated above, the adhesive composition continues tocure over time through the reaction of the isocyanate groups of theprepolymer of Part A and the hydroxyl groups of the polyol of Part B.

The adhesive composition, upon exposure to radiation, preferablyexhibits a green strength suitable to permit handling and subsequentprocessing of the laminate. One useful method of measuring greenstrength is lap shear. Preferably the adhesive composition exhibits alap shear of at least 25 grams/square inch (g/in²), at least 100 g/in²,at least 500 g/in², at least about 600 g/in², or even at least about 800g/in², and a probe tack of at least 20 g/in², at least about 25 g/in²,or even at least about 30 g/in² after exposure to ultraviolet radiation.The cured adhesive composition also preferably exhibits a peel force ofat least 25 g/lineal inch, or even a destructive bond to the substrateto which it is bonded.

Part A

The first part, Part A, of the dual cure composition includes theradiation polymerizable polyisocyanate prepolymer (preferably a(meth)acrylate functional, polyisocyanate prepolymer) and polyisocyanatemonomer. Part A preferably includes from at least about 40% by weight,at least about 50% by weight, at least about 60% by weight, no greaterthan about 90% by weight, or even no greater than about 80% by weightradiation polymerizable polyisocyanate prepolymer, and at least about10% by weight, at least 15% by weight, at least 20% by weight, at least30% by weight, at least 40% by weight, no greater than 60% by weight, oreven no greater than 50% by weight polyisocyanate monomer.

Radiation Polymerizable Polyisocyanate Prepolymer

The radiation polymerizable, polyisocyanate prepolymer includesradiation curable functional groups and isocyanate functional groups.The functional groups are located pendant, terminal or a combinationthereof on the prepolymer. Preferably the functional groups are locatedterminally on the prepolymer, i.e., the prepolymer is end capped withfunctional groups. The radiation polymerizable, polyisocyanateprepolymer preferably includes at least about 5% by weight, at leastabout 10% by weight, no greater than about 20% by weight, or no greaterthan about 18% by weight isocyanate functional groups, and an amount ofradiation polymerizable functional groups sufficient to provide acomposition that, upon exposure to radiation, exhibits a green strengthsuitable for subsequent processing.

The ratio of the equivalents of radiation polymerizable functionalgroups to isocyanate groups in Part A preferably is from 0.1:1 to about5:1, from 0.5:1 to about 4:1, from 0.6:1 to about 3:1, or even about1:1. The average functionality of the radiation polymerizable,polyisocyanate prepolymer is preferably at least about 1.8, about 2, nogreater than 8, or even no greater than about 4, and the number averagemolecular weight of the radiation polymerizable, polyisocyanateprepolymer is preferably from about 200 to about 10,000, from about 400to about 50,000, or even from about 600 to about 2,000.

The radiation polymerizable, polyisocyanate prepolymer is preferablyprepared by reacting a compound that includes an active hydrogen and aradiation polymerizable functional group with a polyisocyanateprepolymer, preferably in the presence of excess isocyanate. Preferablythe compound that includes an active hydrogen and a radiationpolymerizable functional group is reacted with the isocyanate functionalprepolymer in an amount such that from about 10% to about 80%, fromabout 20% to about 70%, or even from about 30% to about 60% of theisocyanate groups on the isocyanate functional prepolymer are replacedwith the compound that includes the active hydrogen and the radiationpolymerizable functional group.

The term “active hydrogen” refers to the active hydrogen on hydroxyl,amine, and mercapto functional groups.

Examples of radiation polymerizable functional groups include acrylate,methacrylate, akenyl groups (e.g., vinyl, allyl, and hexenyl), vinylethers, vinyl esters, vinyl amides, maleate esters, fumarate esters, andstyrene functional groups and combinations thereof.

Suitable compounds that include an active hydrogen and a radiationpolymerizable functional group include, e.g., hydroxyalkyl acrylates andmethacrylates (e.g., 2-hydroxyethylacrylate (HEA),2-hydroxyethylmethylacrylate (HEMA), 2-hydroxypropylacrylate,3-hydroxypropylacrylate (HPA) and 2-hydroxypropyl methacrylate,3-hydroxypropyl methacrylate, 1,3-dihidroxypropylacrylate and2,3-dihidroxypropylacrylate and methacrylate, 2-hydroxyethylacrylamideand methacrylamide, 2-hydroxybutyl (meth)acrylate,4-hydroxybutyl(meth)acrylate, 2-hydroxy-3-phenyloxypropyl(meth)acrylate, 1,4-butanediol mono(meth)acrylate, 2-hydroxyalkyl(meth)acryloyl phosphates, 4-hydroxycyclohexyl(meth)acrylate,1,6-hexanediol mono(meth)acrylate, neopentyl glycol mono(meth)acrylate,trimethylolpropane di(meth)acrylate, trimethylolethane di(meth)acrylate,pentaerythritol tri(meth)acrylate, dipentaerythritolpenta(meth)acrylate; N-alkyl-N-hydroxyethylacrylamides andmethacrylamides, hydroxyethyl-betacarboxyethylacrylate, hydroxyhexylacrylate, and hydroxyoctyl methacrylate and mixtures thereof.

Useful hydroxyethylacrylates and hydroxypropylacrylates are commerciallyavailable from Dow Chemical (Midland Mich.) and Osaka Organic ChemicalIndustry Ltd. (Osaka, Japan). Useful hydroxybutyl acrylates arecommercially available from Osaka Organic Chemical Industry Ltd. Usefulhydroxy polyester acrylates are commercially available under the TONEMONOMER M-100 trade designation from Dow Chemical Company and VISCOAT2308 from Osaka Organic Chemical Industry Ltd. Useful hydroxy polyetheracrylates are commercially available under the ARCOL R-2731 tradedesignation from Bayer Chemicals (Pittsburgh, Pa.).

The polyisocyanate prepolymer is the reaction product of apolyisocyanate, and a polyol having a molecular weight of at least 500g/mole, at least 1000 g/mole, no greater than 4000 g/mole, or even nogreater than 2000 g/mole. The amount of polyisocyanate and polyol in thereaction mixture is such that the ratio of isocyanate to hydroxyl groupsis at least 2:1. The resulting polyisocyanate prepolymer is free ofhydroxyl groups and has a molecular weight of at least 500 g/mole, atleast 1000 g/mole, or even no greater than 6000 g/mole.

Polyisocyanates useful in the preparation of the polyisocyanateprepolymer have at least two isocyanate groups and include, e.g.,aliphatic, cyclopaliphatic, araliphatic, arylalkyl, alkylaryl, andaromatic isocyanates, and mixtures thereof, diisocyanates,triisocyanates, tetraisocyanates, and mixtures thereof.

Useful aromatic polyisocyanates include, e.g., diphenylmethanediisocyanate compounds (MDI) including its isomers, carbodiimidemodified MDI, diphenylmethane 4,4′-diisocyanate, diphenylmethane2,2′-diisocyanate, diphenylmethane 2,4′-diisocyanate, oligomericmethylene isocyanates having the formula

where n is an integer of from 2 to 5, and mixtures thereof; toluenediisocyanate (TDI) including the isomers thereof, isomers of naphthalenediisocyanate, isomers of triphenylmethane triisocyanate, and mixturesthereof.

Other suitable diisocyanates include, e.g., 1,3-cyclopentanediisocyanate, 1,4-cyclohexane diisocyanate, 1,3-cyclohexanediisocyanate, hydrogenated MDI (i.e., dicyclohexylmethane diisocyanate,H₁₂-MDI), methyl 2,4-cyclohexanediisocyanate, methyl2,6-cyclohexanediisocyanate, 1,4-bis(isocyanatomethyl)cyclohexane,1,3-bis(isocyanatomethyl)cyclohexane, 4,4′-diphenyl diisocyanate,4,4′-toluidine diisocyanate, dianilidine diisocyanate, 4,4′-diphenylether diisocyanate, 1,3-xylylene diisocyanate including1,3-diisocyanato-o-xylene, 1,3-diisocyanato-p-xylene and1,3-diisocyanato-m-xylene, 1,4-xylylene diisocyanate,omega,omega′-diisocyanato-1,4-diethylbenzene, isomers oftetramethylxylylene diisocyanate, dialkyldiphenylmethane diisocyanates,tetraalkyldiphenylmethane diisocyanates, 4,4′-dibenzyl diisocyanate,1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate and mixturesthereof.

Examples of additional suitable diisocyanates include1,2-diisocyanatoethane, 1,3-diisocyanatopropane,1,2-diisocyanatopropane, 1,4-diisocyanatobutane,1,5-diisocyanatopentane, 1,6-diissocyanatohexane, bis(3-isocyanatopropyl)ether, bis(3-isocyanatopropyl)sulfide,1,7-diisocyanatoheptane, 1,5-diisocyanato-2,2-dimethylpentane,1,6-diisocyanate -3-methoxyhexane, 1,8-diisocyanatoctane,1,5-diisocyanato-2,2,4-trimethylpentane, 1,9-diisocyanatononane,1,10-diisocyanatopropyl ether of 1,4-butylene glycol,1,11-diisocyanatoundecane, 1,12-diisocyanatododecane,bis(isocyanatohexyl)sulfide, 2,4-diisocyanto-1-chlorobenzene,2,4-diisocyanato-1-nitrobenzene, 2,5-diisocyanato-1-nitrobenzene,m-phenylene diisocyanate, 1-methoxy-2,4-phenylene diisocyanate,1-methoxy-2,4-phenylene diisocyanate, 3,3′-dimethyl-4,4′-diphenylmethanediisocyanate, 1-methyl-2,4-diisocyanatocyclohexane,1,6-diisocyanato-2,2,4-trimethylhexane,1,6-di-isocyanato-2,4,4-trimethylhexane,1-isocyanatomethyl-3-isocyanato-1,5,5-trimethylcyclohexane (IPDI),chlorinated and brominated diisocyanates, phosphorus-containingdiisocyanates, 4,4′-diisocyanatophenylperfluoroethane,tetramethoxybutane-1,4-diisocyanate, bisisocyanatoethyl phthalate;polyisocyanates containing reactive halogen atoms (e.g.,1-chloromethylphenyl-2,4-diisocyanate,1-bromoethylphenyl-2,6-diisocyanate, and 3,3-bischloromethylether-4,4′-diphenyldiisocyanate); sulfur-containing polyisocyanates;dimeric fatty acid diisocyanates, and combinations thereof. Particularlypreferred diisocyanates include 2,4′-methylene diphenyl diisocyanate and4,4-methylene diphenyl diisocyanate.

Examples of suitable triisocyanates include 4,4′,4″-triphenylmethanetriisocyanate and 2,4,6-toluene triisocyanate. One example of atetraisocyanates is 4,4′-dimethyl-2,2′-5,5′-diphenylmethanetetraisocyanate. Another suitable isocyanate is polymethylenepolyphenylene polyisocyanate.

Other useful isocyanates are disclosed in, e.g., U.S. Pat. Nos.6,387,449, 6,355,317, 6,221,978, 4,820,368, 4,808,255, 4,775,719, and4,352,858, and incorporated herein.

Useful commercially available aromatic isocyanates include, e.g.,aromatic isocyanates available under the trade designations MONDUR MLfrom Bayer Chemicals (Pittsburgh, Pa.), ISONATE 50 OP and ISONATE 125Mfrom Dow Chemical Company (Midland, Mich.), and LUPRANATE MI from BASF(Germany).

The polyol used in the formation of the polyisocyanate prepolymer has atleast two hydroxyl (OH) groups and a number average molecular weight ofat least 500 g/mole, at least about 1000 g/mole, no greater than 4000g/mole, no greater than about 2000 g/mole, from 500 g/mole to about 2000g/mole, or even from 500 g/mole to about 1000 g/mole. Such polyolsinclude polyester polyols, polyether polyols, polycarbonates andpolyacetals.

Polyester polyols can be prepared by polycondensation of acid and/oranhydride with at least one alcohol, e.g., polycondensation ofpolycarboxylic acid or anhydride and polyol. Suitable polycarboxylicacids for use in preparing polyester polyols include, e.g., aliphatic,cycloaliphatic, araliphatic, aromatic and heterocyclic polycarboxylicacids and anhydrides. Examples of such polycarboxylic acids andanhydrides include succinic acid, adipic acid, suberic acid, azelaicacid, sebacic acid, cyclohexanediacid, glutaric acid, phthalic acid,isophthalic acid, terephthalic acid, trimellitic acid, phthalicanhydride, tetrahydrophthalic anhydride, hexahydro-phthalic anhydride,tetrachlorophthalic anhydride, endomethylenetetrahydrophthalicanhydride, glutaric anhydride, maleic acid, maleic anhydride, fumaricacid, dimeric fatty acids, trimeric fatty acid, trimellitic acid,trimellitic anhydride, and combinations thereof.

Useful polyols for preparing polyester polyols include aliphatic polyols(e.g., neopentylglycol, ethylene glycol, 1,2-propanediol,1,3-propanediol, 1,4-butanediol, 1,3-butanediol, 2,3-butanediol,1,4-butenediol, 1,4-butynediol, 1,5-pentanediol, 1,6-hexanediol,hexenediols, hexynediols, 1,7-heptanediol, heptenediols, hepthynediols,1,8-octanediol, octenediols, and octynediols), cyclohexane dimethanol,glycerol, trimethylolpropane, pentaerythritol, sorbitol, and glucose,and mixtures thereof.

Useful polyether polyols include the reaction product of polyols andpolyalkylene oxides. Useful polyols for preparing polyether polyolsinclude ethylene glycol, propylene glycol, butanediols, hexanediols,glycerols, trimethylolethane, trimethylolpropane, and pentaerythritol,and mixtures thereof. Useful alkylene oxides for preparing polyetherpolyols include ethylene oxide, propylene oxide and butylenes oxide andmixtures thereof.

Polyisocyanate Monomer

Part A also includes excess polyisocyanate monomer. Excesspolyisocyanate monomer is preferably present in the adhesive compositionan amount sufficient to achieve an adhesive composition that exhibits adestructive peel when tested according to the Peel Adhesion Test Method.Suitable polyisocyanate monomers include the polyisocyanates set forthabove and incorporated herein.

Part B

The second part, Part B, of the dual cure composition includes polyol,and preferably photoinitiator. Part B preferably includes from about 70%by weight to about 100% by weight, from about 80% by weight to about100% by weight, or even from about 90% by weight to about 100% by weightof the polyol, and from 0% by weight to about 10% by weight, from 0.2%by weight to about 5% by weight, or even from 0.5% by weight to 1% byweight photoinitiator.

Polyol

Suitable polyols for Part B, as well as for use in the preparation ofthe polyisocyanate prepolymer described above, include, e.g., diols,triols and mixtures thereof. Preferred polyols include polyesterpolyols, polyether polyols, polyolefin diols, polydiene block polyols,and combinations thereof. Preferred polyols have a functionality of atleast about 1.5, at least about 2, at least about 3, no greater than4.0, no greater than 3.5. Preferred polyols have a Tg less than 10° C.,or even less than 0° C., and a number average molecular weight of atleast about 500 g/mole to about 5000 g/mole, or even from about 750g/mole to about 2000 g/mole.

Useful classes of polyols include, e.g., polyester polyols including,e.g., lactone polyols and the alkyleneoxide adducts thereof, and dimeracid-based polyester polyols, specialty polyols including, e.g.,polybutadiene polyols, hydrogenated polybutadiene polyols, polycarbonatepolyols, hydroxy alkyl derivatives of bisphenol A (e.g.,bis(2-hydroxyethyl) bisphenol A), polyether polyols including, e.g.,polythioether polyols, and fluorinated polyether polyols, acrylicpolyols, alkylene oxide adducts of polyphenols, polytetramethyleneglycols, functional glycerides (e.g., castor oil), and polyhdroxysulfide polymers.

Useful polyester polyols are prepared from the reaction product ofpolycarboxylic acids, their anhydrides, their esters or their halides,and a stoichiometric excess polyhydric alcohol. Suitable polycarboxylicacids include dicarboxylic acids and tricarboxylic acids including,e.g., aromatic dicarboxylic acids, anhydrides and esters thereof (e.g.terephthalic acid, isophthalic acid, dimethyl terephthalate, diethylterephthalate, phthalic acid, phthalic anhydride,methyl-hexahydrophthalic acid, methyl-hexahydrophthalic anhydride,methyl-tetrahydrophthalic acid, methyl-tetrahydrophthalic anhydride,hexahydrophthalic acid, hexahydrophthalic anhydride, andtetrahydrophthalic acid), aliphatic dicarboxylic acids and anhydridesthereof (e.g. maleic acid, maleic anhydride, succinic acid, succinicanhydride, glutaric acid, glutaric anhydride, adipic acid, pimelic acid,suberic acid, azelaic acid, sebacic acid, chlorendic acid,1,2,4-butane-tricarboxylic acid, decanedicarboxylic acid,octadecanedicarboxylic acid, dimeric acid, dimerized fatty acids,trimeric fatty acids, and fumaric acid), and alicyclic dicarboxylicacids (e.g. 1,3-cyclohexanedicarboxylic acid, and1,4-cyclohexanedicarboxylic acid).

Examples of suitable polyols from which polyester polyols can be derivedinclude aliphatic polyols, e.g., ethylene glycols, propane diols (e.g.,1,2-propanediol and 1,3-propanediol), butane diols (e.g.,1,3-butanediol, 1,4-butanediol, and 1,7-butanediol), 1,3-butenediol,1,4-butenediol, 1,4-butynediol, pentane diols (e.g., 1,5-pentanediol),pentenediols, pentynediols, 1,6-hexanediol, 1,8-octanediol,1,10-decanediol, neopentyl glycol, diethylene glycol, triethyleneglycol, tetraethylene glycol, polyethylene glycols, propylene glycol,polypropylene glycols (e.g., dipropylene glycol and tripropyleneglycol), neopentylglycol, 1,4-cyclohexanedimethanol,1,4-cyclohexanediol, dimer diols, bisphenol A, bisphenol F, hydrogenatedbisphenol A, hydrogenated bisphenol F, glycerol, tetramethylene glycol,polytetramethylene glycol, 3-methyl-1,5-pentanediol, 1,9-nonanediol,2-methyl-1,8-octanediol, and trimethylolpropane, pentaerythritol,sorbitol, glucose, and combinations thereof.

Examples of useful polyester polyols include polyglycol adipates,polyethylene terephthalate polyols, polycaprolactone polyols andpolycaprolactone triols.

Suitable commercially available polyols include, e.g., polyester polyolsavailable under the DESMOPHEN series of trade designations including,e.g., DESMOPHEN XF-7395-200, DESMOPHEN S-1011-P-210, DESMOPHENS-1011-110 and DESMOPHEN S-1011-55 from Bayer Chemicals (Pittsburgh,Pa.), dimer acid-based polyester polyols available under the PRIPLASTseries of trade designations including, e.g., PRIPLAST 3187, 3190, 3196,and 3197 from UNIQEMA (New Castle, Del.), polybutadiene polyolsavailable under the trade designations POLYBD R-20LM, R-45HT, and R-45Mfrom Atofina Chemicals, Inc. (Exton, Pa.), and hydrogenatedpolybutadiene polyols available under the trade designation POLYTAILfrom Mitsubishi Chemical Corp. (Japan).

Suitable polyether polyols include the products obtained from thepolymerization of a cyclic oxide, e.g., ethylene oxide, propylene oxide,butylene oxide, and tetrahydrofuran, or by the addition of one or moresuch oxides to polyfunctional initiators having at least two activehydrogens, e.g., water, polyhydric alcohols (e.g., ethylene glycol,propylene glycol, diethylene glycol, cyclohexane dimethanol, glycerol,trimethylol-propane, pentaerythritol and Bisphenol A), ethylenediamine,propylenediamine, triethanolamine, and 1,2-propanedithiol. Particularlyuseful polyether polyols include, e.g., polyoxypropylene diols andtriols, poly(oxyethylene-oxypropylene)diols and triols obtained by thesimultaneous or sequential addition of ethylene oxide and propyleneoxide to appropriate initiators and polytetramethylene ether glycolsobtained by the polymerization of tetrahydrofuran.

Photoinitiator

The composition also includes photoinitiator. Photoinitiator can bepresent in any part of the composition including, e.g., Part A, Part B,and Part C, added as a separate component, and combinations thereof.Preferred photoinitiators are capable of promoting free radicalpolymerization, crosslinking, or both, of the ethylenically unsaturatedmoiety on exposure to radiation of a suitable wavelength and intensity.The photoinitiator can be used alone, or in combination with a suitabledonor compound or a suitable cointiator. The photoinitiator and theamount thereof are preferably selected to achieve a uniform reactionconversion, as a function of the thickness of the composition beingcured, as well as a sufficiently high degree of total conversion so asto achieve the desired initial handling strength (i.e., green strength).

Useful photoinitiators include, e.g., “alpha cleavage type”photoinitiators including, e.g., benzoin, benzoin acetals (e.g., benzyldimethyl ketal), benzoin ethers (e.g., benzoin ethyl ether, benzoinisopropyl ether, and benzoin isobutyl ether), hydroxy alkyl phenylketones (e.g., 1-hydroxycyclohexyl phenyl ketone,2-hydroxy-2-methyl-1-phenylpropan-1-one, and1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one), benzoylcyclohexanol, dialkoxy acetophenone derivatives (e.g.,2,2-diethoxyacetophenone), acylphosphine oxides (e.g.,bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide,bis(2,6-dimethoxybenzoyl)-(2,4,4-trimethylpentyl)phosphine oxide, and2,4,4-trimethylbenzoyl diphenylphosphine oxide), methyl thio phenylmorpholino ketones (e.g., 2-methyl-1-4(methylthio) andphenyl-2-morpholino-1-propanone), and morpholino phenyl amino ketones;hydrogen abstracting photoinitiators, which include a photoinitiator anda coinitiator, based on benzophenones, thioxanthones, benzyls,camphorquinones, and ketocoumarins; and combinations thereof. Preferredphotoinitiators include acylphosphine oxides including, e.g.,bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide,bis(2,6-dimethoxybenzoyl)-(2,4,4-trimethylpentyl)phosphine oxide, and2,4,4-trimethylbenzoyl diphenylphosphine oxide.

Other suitable photoinitiators include, e.g., organic peroxides, azocompounds, quinones, nitroso compounds, acryl halides, hydrozones,mercapto compounds, pyrylium compounds, triacrylimidazoles,bisimidazoles, chloroalkytriazines, benzoin ethers, benzil ketals,thioxanthones, and acetophenone derivatives, and mixtures thereof.

Useful commercially available photoinitiators are available under thefollowing trade designations IRGACURE 369 morpholino phenyl aminoketone, IRGACURE 819 bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide,IRGACURE CGI 403bis(2,6-dimethoxybenzoyl)-(2,4,4-trimethylpentyl)phosphine oxide,IRGACURE 651 benzyl dimethyl ketal, IRGACURE 184 1-hydroxycyclohexylphenyl ketone, and IRGACURE 29594-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-methylpropyl)ketone, DAROCUR 11732-hydroxy-2-methyl-1-phenyl-propan-1-one, which is also known ashydroxymethylphenylpropanone, DAROCUR 4265 50:50 blend of2-hydroxy-2-methyl-1-phenylpropan-1-one and2,4,6-trimethylbenzoyldiphenylphosphine oxide, and CGI1700 25:75 blendof bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine and2-hydroxy-2-methyl-1-phenylpropan-1-one, all of which are available fromCiba Specialty Chemicals (Ardsley, N.Y.)

The photoinitiator is preferably present in an amount sufficient toprovide the desired rate of photopolymerization. The amount will depend,in part, on the light source, the thickness of the layer to be exposedto radiant energy and the extinction coefficient of the photoinitiatorat the wavelength. Typically, the photoinitiator component will bepresent in an amount of at least about 0.01% by weight, at least about0.1% by weight, at least about 0.2% by weight, no greater than about 10%by weight, or even no greater than about 5% by weight.

Part C

The composition can optionally include a component that includes atleast two radiation polymerizable functional groups where the functionalgroups are polymerizable by UV or electron beam radiation, i.e., Part C.The component of Part C can include any level of radiation polymerizablepolyfunctionality including mono-, di-, tri-, tetra-, and higherfunctionality. Suitable examples of components with multiple radiationpolymerizable functional groups include (meth)acrylate esters including,e.g., esters of acrylic acid and methacrylic acid prepared from acrylicacid and/or methacrylic acid and aliphatic alcohols, aromatic polyols,aliphatic polyols, cylcoaliphatic polyols, and combinations thereof,(meth)acrylate esters of polyether alcohols, urethane (meth)acrylateoligomers, epoxy(meth)acrylate oligomers, and combinations thereof.

Useful acrylate esters of aliphatic alcohols include, e.g., isobornyl(meth)acrylate, 2-ethoxyethoxy ethyl (meth)acrylate, and combinationsthereof. Useful acrylate esters of aliphatic diols include, e.g.,neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)-acrylate,trimethylolpropane tri(meth)acrylate, pentaerythritoltetra(meth)acrylate, and (meth)acrylate esters of sorbitol and of othersugar alcohols. These (meth)acrylate esters of aliphatic andcycloaliphatic diols may be modified with an aliphatic ester or with analkylene oxide. The acrylates modified by an aliphatic ester include,e.g., neopentyl glycol hydroxypivalate di(meth)acrylate,caprolactone-modified neopentyl glycol hydroxypivalatedi(meth)acrylates, and combinations thereof. The alkylene oxide-modifiedacrylate compounds include, e.g., ethylene oxide-modified neopentylglycol di(meth)acrylates, propylene oxide-modified neopentyl glycoldi(meth)acrylates, ethylene oxide-modified 1,6-hexanedioldi(meth)acrylates or propylene oxide-modified 1,6-hexanedioldi(meth)acrylates, and combinations thereof.

Suitable acrylate monomers derived from polyether polyols include, e.g.,neopentyl glycol-modified trimethylolpropane di(meth)acrylates,polyethylene glycol di(meth)acrylates, polypropylene glycoldi(meth)acrylates and the like. Trifunctional and higher polyfunctionalacrylate monomers include, e.g., trimethylolpropane tri(meth)acrylate,pentaerythritol tri(meth)acrylate, dipentaerythritoltetra(meth)acrylate, dipentaerythritol penta(meth)acrylate,dipentaerythritol hexa(meth)acrylate, caprolactone-modifieddipentaerythritol hexa(meth)acrylate, pentaerythritoltetra(meth)acrylate, tris[(meth)acryloxyethyl]isocyanurate,caprolactone-modified tris[(meth)acryloxyethyl]isocyanurates ortrimethylolpropane tetra(meth)acrylate, and combinations thereof.

Suitable polyfunctional (meth)acrylate monomers include, e.g.,tripropylene glycol diacrylate, neopentyl glycol propoxylatedi(meth)acrylate, trimethylolpropane tri(meth)acrylate, andpentaerythritol triacrylate, and combinations thereof.

Other Additives

The composition can also include other additives including, e.g.,antioxidants, plasticizers, tackifying agents, adhesion promoters,non-reactive resins, ultraviolet light stabilizers, catalysts, rheologymodifiers, biocides, corrosion inhibitors, dehydrators, organicsolvents, colorants (e.g., pigments and dyes), fillers, surfactants,flame retardants, waxes, and mixtures thereof. These components, whenpresent, are preferably selected to have limited UV absorption tomaximize the amount of light transmitted through the material andavailable for the photoinitiator molecules to initiate thephotopolymerization process.

Suitable plasticizers include, e.g., phthalates, benzoates,sulfonamides, and mixtures thereof, and epoxidized soybean oil. Usefulsources of dioctyl and diisodecyl phthalate include those availableunder the trade designations JAYFLEX DOP and JAYFLEX DIDP from ExxonChemical. Useful dibenzoates are available under the trade designationsBENZOFLEX 9-88, BENZOFLEX 50 and BENZOFLEX 400 from Velsicol ChemicalCorporation. Soybean oil is commercially available, e.g., from UnionCarbide Corporation under the trade designation FLEXOL EPO.

Plasticizer, when present, is preferably present in the composition inan amount of from about 0.25% by weight to about 10% by weight, nogreater than about 5% by weight, no greater than about 3% by weight, oreven from about 0.5% by weight to 2% by weight.

Suitable fillers include, e.g., fumed silica, precipitated silica, talc,calcium carbonates, carbon black, alumina silicates, clay, zeolites,ceramics, mica, titanium dioxide, and combinations thereof. Whenpresent, the composition preferably includes filler in an amount of atleast 0.5% by weight, from about 1% by weight to about 50% by weight, oreven from about 5% by weight to about 10% by weight.

The composition can optionally include thermoplastic polymers includinge.g., ethylenevinyl acetate, ethylene-acrylic acid, ethylenemethacrylateand ethylene-n-butyl acrylate copolymers, polyvinyl alcohol,hydroxyethylcellulose, hydroxylpropylcellulose, polyvinyl methyl ether,polyethylene oxide, polyvinylpyrrolidone, polyethyloxazolines, starch,cellulose esters, and combinations thereof.

Method of Manufacturing

The composition is well suited for manufacturing laminates. Any suitablemethod of making laminates can be used. One useful method includesapplying adhesive in the liquid state to a film that is to be bonded toform a laminate. The adhesive may be applied using any suitable coatingprocess including, e.g., air knife, trailing blade, spraying, brushing,dipping, doctor blade, roll coating, gravure coating, offset gravurecoating, rotogravure coating, and combinations thereof. Useful coatingtemperatures range from 65° F. to 170° F. The coating weight of theadhesive may vary broadly depending on the properties desired of thelaminate. Useful adhesive coating weights include, e.g., from 0.5 pounds(lb) per 3000 square feet (ft²) (i.e., a ream) to about 4 lbs/ream, oreven from about 0.5 lbs/ream to 1.5 lbs/ream.

The coated film is then transferred to a radiation zone in which thepolymerization reaction, i.e., the crosslinking of the individualcomponents, is initiated by exposing the adhesive composition toultraviolet radiation (i.e., radiation in the range from about 200 nm toabout 400 nm). The adhesive of the invention develops adhesion, forexample, contact adhesion, but preferably pressure-sensitive adhesion,by virtue of the radiation and the associated crosslinking reaction ofthe individual components present in the adhesive. The amount ofradiation necessary to cure or partially cure the composition willdepend on a variety of factors including, e.g., the angle of exposure tothe radiation, the thickness of the coating, the amount of polymerizablegroups in the coating composition, and the type and amount ofphotoinitiator. Typically, a UV light source with a wavelength fromabout 200 nm to about 400 nm is directed at the adhesive coating that isbeing transported on a conveyor system that proves a rate of passagepast the UV source appropriate for the radiation absorption profile ofthe composition. Useful sources of UV light include, e.g., extra highpressure mercury lamps, high pressure mercury lamps, medium pressuremercury lamps, low intensity fluorescent lamps, metal halide lamps,microwave powered lamps, xenon lamps, laser beam sources including,e.g., excimer lasers and argon-ion lasers, and combinations thereof.

Following the radiation procedure, the first film coated with theirradiated adhesive composition is contacted with a second film, with orwithout the application of pressure, to form a laminate. The secondsubstrate may be of the same or different composition relative to thefirst substrate. The second substrate can be applied to the adhesive byapplication of pressures and temperatures commonly used in filmlaminating equipment.

This procedure is particularly advantageous for the mutual adhesivebonding of two films that are impervious to radiation.

The bonding and laminating procedure described may be repeated a numberof times, so that it is possible to produce laminates which consist ofmore than two bonded layers.

Another suitable method of making a laminate includes coating theadhesive composition on a first substrate, contacting the coatedadhesive composition with a second substrate, and exposing the adhesivecomposition or the construction as a whole to radiation. The adhesivecomposition can be exposed to radiation before, during, after or acombination thereof, contacting the adhesive composition with a secondsubstrate.

Useful substrates include flexible films including, e.g., metal foils(aluminum foil), polymer films and metallized polymer films preparedfrom polymers including, e.g., polyolefins (e.g., polypropylene,polyethylene, low density polyethylene, linear low density polyethylene,high density polyethylene, polypropylene, and oriented polypropylene;copolymers of polyolefins and other comonomers) metallized polyolefins(e.g., metalized polypropylene), metalized polyether terephthalate,ethylene-vinyl acetates, ethylene-methacrylic acid ionomers,ethylene-vinyl-alcohols, polyesters, e.g. polyethylene terephthalate,polycarbonates, polyamides, e.g. Nylon-6 and Nylon-6,6, polyvinylchloride, polyvinylidene chloride, cellulosics, and polystyrene, andretortable packaging laminate materials. The thickness of a film mayvary, but flexible films typically have a thickness of less than about0.25 millimeters, e.g. from about 10 micrometers to about 150micrometers, more typically from about 8 micrometers to about 100micrometers. The surface of the substrate can be surface treated toenhance adhesion using any suitable method including, e.g., coronatreatments, chemical treatments and flame treatments.

Other suitable substrates include, e.g. woven webs, non-woven webs,paper, paperboard, and cellular flexible sheet materials (e.g.,polyethylene foam, polyurethane foam and sponge and foam rubber). Wovenand non-woven webs can include fibers including, e.g., cotton,polyester, polyolefin, polyamide, and polyimide fibers.

The substrate can be constructed to exhibit many useful properties.Preferably the substrate exhibits properties useful for flexiblepackaging and retortable packaging. Such properties include, e.g., hightensile strength, vapor barrier properties, flexibility, rigidity,resistance to thermal degradation and combinations thereof.

The invention will now be described by way of the following examples.

EXAMPLES

Test Procedures

Test procedures used in the examples include the following.

% NCO

The isocyanate percentage (i.e., % NCO) present in the adhesivecomposition is determined by first dissolving the prepolymer in toluene,reacting a predetermined volume of the prepolymer/toluene solution witha predetermined volume of a dibutylamine solution. The amine reacts withthe isocyanate groups. The excess amine is then titrated with apredetermined solution of hydrogen chloride. The volume of the hydrogenchloride solution is then used to calculate the % NCO present in thecomposition.

Viscosity

The viscosity of the adhesive composition is determined at roomtemperature using a Brookfield Thermosel viscometer with a number 27spindle.

Peel Adhesion Test Method

The peel force is determined according to ASTM D1876-01 entitled,“Standard Test Method for Peel Resistance of Adhesives,” which isincorporated herein. The adhesive is coated on a 1.5 mil thickmetallized polyethylene terephthalate film substrate at a coating weightfrom 1 lbs per ream to 7 lbs per ream. The coated adhesive compositionis then exposed to radiation from a medium pressure mercury lamp havinga power of 300 watts per inch at a conveyor speed of 100 feet perminute. The partially cured composition is then laminated with thesecond substrate, a 1.5 mil thick polyethylene film. The peel speed is12 inches per minute. The results are reported in grams per lineal inch.

Lap Shear Test Method

The lap shear is determined according to ASTM D3163 in which the testspecimen is constructed to have 1 mil coating of adhesive on a 2 milthick polyethylene terephthalate substrate laminated to a second 2 milthick polyethylene terephthalate substrate with a 1 inch×1 inchsubstrate overlap. The coated composition is first exposed to radiationfrom a medium pressure mercury lamp having a power of 300 watts per inchat a conveyor speed of 100 feet per minute. The partially curedcomposition is then laminated with the second substrate. The MaximumLoad is determined and results are reported in units of g/in².

Probe Tack Test Method

The probe tack test is determined by lowering an eight millimeter (mm)diameter spherical probe onto a sample at 100 grams of force for aperiod of 1 second using an Instron Model 5542 Universal Tester. Thesample is a 1 mil thick coating of adhesive on a 2 mil thick PET filmsubstrate. The probe is then withdrawn at a rate of 1000 mm/second. Theforce that it takes to pull the probe off the adhesive is referred tothe “Pull Off” force. The maximum Pull Off force is measured andreported in units of g/in².

Examples 1-8

Part A is prepared by charging DESMOPHEN S-1011-210 polyester polyol(Bayer Corporation, Pittsburg, Pa.) to a reactor and heating to 130° F.A nitrogen purge is started and continued during the process. LUPRANATEMI monomeric 2,4′-diphenylmethane diisocyanate (MDI) (BASF Corporation,Syandotte, Mich.) is then added to the reactor in an amount sufficientto achieve at a stoichiometric NCO/OH ratio of from 2/1 (NCO/OH) to2.5/1 (NCO/OH). The mixture is agitated and the temperature is raised tofrom 160° F. to 170° F. The reaction is complete in from one to twohours. The % NCO is checked periodically to determine if the reaction iscomplete, i.e., the target % NCO is obtained. The agitation is thenstopped and 2-hydroxyethyl acrylate (HEA) (Dow Chemical Company,Midland, Mich.) is added to the reactor and allowed to react whilemaintaining the temperature from 160° F. to 170° F. The second reactionis complete in from 1 to 2 hours. The % NCO is checked to determine ifthe reaction is complete. The agitation is then stopped and additionalLUPRANATE MI monomeric MDI is added to the reactor. The agitation isthen restarted and continued until the mixture is homogeneous. Theamounts of polyester polyol, MDI, and HEA used in Part A are set forthin Table 1.

Part B is prepared by combining 97.5% DESMOPHEN XF-7395-200 polyesterpolyol with a hydroxyl number of approximately 200 and 2.5% DAROCUR 1173photoinitiator.

Part A is mixed with Part B to provide a stoichiometric ratio of NCO:OHof 1.4:1.0.

The adhesive composition is then coated on a 1.5 mil thick metallizedpolyethylene terephthalate film substrate at a coating weight of 1 lbper ream. The coated adhesive composition is then exposed to radiationfrom a medium pressure mercury lamp having a power of 300 watts per inchat a conveyor speed of 100 feet per minute. The partially curedcomposition is then laminated with the second substrate, a 1.5 mil thickpolyethylene film.

The expected viscosity at 70° F., and peel strength at 0 minutes, 24hours, and 48 hours, of the adhesive compositions of Examples 1-8 areset forth in Table 1 below. TABLE 1 Component Example 1 Example 2Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Polyester 5050 50 50 50 50 50 50 polyol (g) MDI (g) 70 70 80 80 80 70 70 70 HEA (g)10 20 20 36 25 15 17 17 Second 73 110 100 155 115 90 75 60 Charge of MDI(g) NCO# 18 18 18 18 18 18 16.36 15 (Theoretical) Viscosity at 5100 35004100 3700 4600 4000 8700 13,600 70° F. Peel Force at 20 38 30 18 34 1830 45 0 hours no cohesive cohesive Sample cohesive more cohesivecohesive (g/lineal inch) cohesive failure failure is over failurecohesive failure failure failure cured failure and does relative nothave to tack Example 1 Peel Force at Destruct Destruct Destruct DestructDestruct Destruct Destruct Destruct 24 hours (g/lineal inch) Peel Forceat Destruct Destruct Destruct Destruct Destruct Destruct DestructDestruct 48 hours (g/lineal inch)

The adhesive composition of Example 1 is tested according to the LapShear and Probe Tack Test Methods. The expected results are reported inTable 2. TABLE 2 Test Before UV Irradiation After UV Irradiation LapShear (g/in²) 22.44 833.21 Probe Tack (g/in²) 6.04 32.38

Comparative Example 1

Part A is prepared as follows. RUCOFLEX 1011-210 polyester polyol in anamount of 46.5 g is charged to a reactor and heated to 130° F. Anitrogen purge is started and continued during the process. LUPRANATE MImonomeric 2,4′-diphenylmethane diisocyanate (MDI) (BASF Corporation,Syandotte, Mich.) in an amount of 46.5 g is then added to the reactor.The mixture is agitated and the temperature is raised to from 160° F. to170° F. The reaction is complete in from one to two hours. The % NCO ischecked periodically to determine if the reaction is complete. Theagitation is then stopped, the temperature is lowered to 140° F., and 7g2-hydroxyethyl acrylate (Dow Chemical Company, Midland, Mich.) is addedto the reactor and allowed to react while maintaining the temperaturefrom 160° F. to 170° F. The second reaction is complete in from 1 to 2hours. The % NCO is checked to determine if the reaction is complete.The agitation is then stopped. The resulting composition is expected tohave a viscosity of 11,470 centipoises at 140° F.

Example 9

Part A is prepared as follows. RUCOFLEX 1011-210 polyester polyol in anamount of 41.5 g is charged to a reactor and heated to 130° F. Anitrogen purge is started and continued during the process. LUPRANATE MImonomeric 2,4′-diphenylmethane diisocyanate (MDI) (BASF Corporation,Syandotte, Mich.) in an amount of 41.5 g is then added to the reactor.The mixture is agitated and the temperature is raised to from 160° F. to170° F. The reaction is complete in from one to two hours. The % NCO ischecked periodically to determine if the reaction is complete. Theagitation is then stopped, the temperature is lowered to 140° F., and 8g 2-hydroxyethyl acrylate (HEA) (Dow Chemical Company, Midland, Mich.)is added to the reactor and allowed to react while maintaining thetemperature from 160° F. to 170° F. The second reaction is complete infrom 1 hour to 2 hours. The % NCO is checked to determine if thereaction is complete. The agitation is then stopped and 9 g ofadditional LUPRANATE MI monomeric MDI is added to the reactor. Theagitation is then restarted and continued until the mixture ishomogeneous.

The composition is expected to have a viscosity of 6037 centipoises at140° F.

Part A of Example 9 and Part A of Comparative Example 1 are eachcombined with Part B of Examples 1-8 to provide a stoichiometric ratioof NCO:OH of 1.4: 1.0. The adhesives are then coated on a 1.5 mil thickmetallized polyethylene terephthalate film substrates at a coatingweight of 1 lb per ream. The coated adhesive compositions are thenexposed to radiation from a medium pressure mercury lamp having a powerof 300 watts per inch at a conveyor speed of 100 feet per minute. Thepartially cured compositions are then laminated with a second substrate,a 1.5 mil thick polyethylene film. The samples are then tested accordingto the Peel Adhesion Test Method. The expected results are reported inTable 3. TABLE 3 Peel Force (g/lineal inch) Comparative Example 1Example 9 At 0 Minutes 26 18 At 24 hours 310 Destruct

Example 10

A number of laminate constructions are prepared using the adhesivecomposition of Example 8. The laminates are prepared by coating theadhesive composition of Example 8 on a first substrate, contacting thecoated adhesive composition with a second substrate, bonding the secondsubstrate to the first substrate through the adhesive composition, andexposing the coated adhesive composition to UV radiation at a power of300 watts/inch at a rate of 100 feet per minute through one of thesubstrates. The peel force is measured according to the Peel AdhesionTest Method. The substrates and the expected results are reported inTable 4.

Control 1

A number of laminate constructions are prepared using the adhesivecomposition of Example 8. The laminates are prepared by coating theadhesive composition of Example 8 on a first substrate, contacting thecoated adhesive composition with a second substrate, and bonding thesecond substrate to the first substrate through the adhesivecomposition. The laminate is then stored at ambient conditions. The peelforce is measured according to the Peel Adhesion Test Method. Thesubstrates and the expected results are reported in Table 4. TABLE 4 24Coating 0 hours 3.5 hours 6 hours hours First Second Weight (g/lineal(g/lineal (g/lineal (g/lineal Laminate Curing Substrate Substrate(lbs/ream) inch) inch) inch) inch) Example 10 UV Paper 0.5 mil PP 1.5 25Destruct Destruct Destruct Example 10 UV 1 mil PE¹ 0.5 mil PP² 1 30Destruct Destruct Destruct Example 10 UV Coated 0.5 mil PP 1.5 0 20(fiber Destruct Destruct paper tear) Control 1 Ambient Paper 0.5 mil PP1.5 0 20 100 Destruct Control 1 Ambient PE 0.5 mil PP 1 0 20 165Destruct Control 1 Ambient Coated 0.5 mil PP 1.5 0  0  20 Destruct paper(fiber tear)

Other embodiments are within the claims.

All of the patents and patent applications cited herein are incorporatedherein, in total, by reference.

1. A method of making a laminate, said method comprising: a) preparingan adhesive composition, said preparing comprising combining a firstpart comprising (meth)acrylate functional, polyisocyanate prepolymer,and polyisocyanate monomer, said first part comprising at least 10% byweight isocyanate functional groups, a second part comprising polyol,and optionally, a third part, at least one of said first part, saidsecond part and said optional third part comprising photoinitiator; b)coating a first flexible substrate with said adhesive composition; c)exposing the adhesive composition to radiation to partially cure saidadhesive composition; and d) contacting said adhesive composition with asecond flexible substrate.
 2. The method of claim 1, wherein said firstpart comprises at least 15% by weight said polyisocyanate monomer. 3.The method of claim 1, wherein said first part comprises at least 30% byweight said polyisocyanate monomer.
 4. The method of claim 1, whereinsaid exposing occurs prior to contacting said adhesive composition withsaid second flexible substrate.
 5. The method of claim 1, wherein saidexposing occurs after contacting said adhesive composition with saidsecond flexible substrate.
 6. The method of claim 1, wherein saidadhesive composition exhibits a viscosity of from 250 centipoise to 5000centipoise at a temperature from 65° F. to 170° F.
 7. The method ofclaim 1, wherein said coating comprises coating said adhesivecomposition at a coating weight of from 0.5 pounds per 3000 square feetto 4 pounds per 3000 square feet.
 8. The method of claim 1, wherein saidadhesive composition exhibits a lap shear strength of at least 25 g/in²after exposure to said radiation.
 9. The method of claim 1, wherein saidadhesive composition exhibits a lap shear strength of at least 100 g/in²after exposure to said radiation.
 10. The method of claim 1, whereinsaid adhesive composition comprises from 5% by weight to 70% by weightsaid (meth)acrylate functional, polyisocyanate prepolymer; at least 7%by weight said polyisocyanate monomer; from 30% by weight to 95% byweight said polyol; and from 0.2% by weight to 10% by weight saidphotoinitiator.
 11. The method of claim 1, wherein said first part ofsaid adhesive composition comprises from 40% by weight to 90% by weightsaid (meth)acrylate functional, polyisocyanate prepolymer, and from 10%by weight to 60% by weight said polyisocyanate monomer.
 12. The methodof claim 1, wherein said first part of said adhesive compositioncomprises from 10% by weight to about 20% by weight isocyanatefunctional groups.
 13. The method of claim 1, wherein said first partcomprises from about 0.5% by weight to about 20% by weight radiationpolymerizable groups.
 14. The method of claim 1, wherein said first partcomprises from about 1% by weight to about 10% by weight radiationpolymerizable groups.
 15. The method of claim 1, wherein the first partand the second part are combined in amounts such that the stoichiometricratio of isocyanate (NCO) to hydroxyl group (OH) (NCO:OH) is from about1:1 to about 2:1.
 16. The method of claim 1, wherein said (meth)acrylatepolyisocyanate prepolymer comprises the reaction product of a) anisocyanate polyurethane prepolymer comprising the reaction product of i)polyol and ii) isocyanate; and b) hydroxy functional (meth)acrylate. 17.The method of claim 16, wherein said hydroxy functional acrylatecomprises hydroxyalkyl (meth)acrylate.
 18. The method of claim 16,wherein said hydroxy functional acrylate comprises hydroxyethylacrylate.
 19. The method of claim 1, wherein said polyol comprisespolyester polyol, polyether polyol, or a mixture thereof.
 20. The methodof claim 1, wherein said polyol has a functionality of at least
 2. 21.The method of claim 1, wherein said polyol has a functionality of nogreater than
 3. 22. The method of claim 1, wherein said adhesivecomposition comprises from 20% by weight to 95% by weight said polyol.23. The method of claim 1, wherein said adhesive composition comprisesfrom 30% by weight to 70% by weight said polyol.
 24. The method of claim1, wherein said adhesive composition comprises from 30% by weight to 70%by weight said (meth)acrylate functional, polyisocyanate prepolymer. 25.The method of claim 1, wherein said adhesive composition comprises from20% by weight to 60% by weight said (meth)acrylate functional,polyisocyanate prepolymer.
 26. The method of claim 1, wherein saidphotoinitiator is selected from the group consisting of dialkoxyacetophenones, hydroxyalkyl phenyl ketones, benzoin ethers, benzoinacetals, acyl phosphine oxides, and combinations thereof.
 27. The methodof claim 1, wherein said photoinitiator comprises a hydroxyl functionalphotoinitiator.
 28. The method of claim 1, wherein at least one of saidfirst and second flexible substrates is a polymer film.
 29. The methodof claim 1, wherein at least one of said first and second flexiblesubstrates is a metallized polymer film.
 30. The method of claim 1,wherein at least one of said first flexible substrate and said secondflexible substrate comprises polyethylene terephthalate, polypropylene,polyethylene, metallized polypropylene, metalized polyethyleneterephthalate, Nylon, and metal foil.
 31. A method of making a laminate,said method comprising: a) coating a first flexible substrate with acomposition comprising (meth)acrylate functional, polyisocyanateprepolymer, at least 7% by weight polyisocyanate monomer, polyol, andphotoinitiator; b) exposing said adhesive composition to radiation topartially cure said adhesive composition; and c) contacting saidadhesive composition with a second flexible substrate.
 32. A method ofmaking a laminate, said method comprising: a) preparing an adhesivecomposition, said preparing comprising combining a first part comprising(meth)acrylate functional, polyisocyanate prepolymer, and at least 15%by weight polyisocyanate monomer, a second part comprising polyol, andoptionally, a third part, at least one of said first part, said secondpart and said optional third part comprising photoinitiator; b) coatinga first flexible substrate with said adhesive composition c) exposingsaid composition to radiation to partially cure said composition; and d)contacting said adhesive composition with a second flexible substrate.33. A method of making a laminate, said method comprising: a) preparingan adhesive composition, said preparing comprising combining(meth)acrylate functional, polyisocyanate prepolymer, polyisocyanatemonomer, the combination of said prepolymer and said monomer comprisingat least 10% by weight isocyanate functional groups based on thecombined weight of said prepolymer and said polyisocyanate monomer,polyol, and photoinitiator; b) coating a first flexible substrate withsaid adhesive composition; c) exposing the adhesive composition toradiation to partially cure said adhesive composition; and d) contactingsaid adhesive composition with a second flexible substrate.
 34. Alaminate comprising: an adhesive composition comprising the reactionproduct of (meth)acrylate functional, polyisocyanate prepolymer,polyisocyanate monomer, the combination of said prepolymer and saidmonomer comprising at least 10% by weight isocyanate functional groupsbased on the combined weight of said prepolymer and said polyisocyanatemonomer, polyol, and photoinitiator; a first flexible substrate; and asecond flexible substrate, said first flexible substrate being bonded tosaid flexible substrate through said adhesive composition.
 35. Alaminate comprising: an adhesive composition comprising the reactionproduct of a (meth)acrylate functional, polyisocyanate prepolymer,polyisocyanate monomer, polyol, and photoinitiator, a first flexiblesubstrate; and a second flexible substrate, said first flexiblesubstrate being bonded to said second flexible substrate through saidadhesive composition, said adhesive composition exhibiting a destructivepeel to at least one of said first and second substrates.
 36. A packagecomprising: a) a food article; and b) the laminate of claim 34 at leastpartially surrounding said food article.